Manufacture of acetylene



R. 1.. HASCHE ,535

MANUFACTURE OF ACETYLENE Fild July 10, 1957 2 Sheets-Sheet 1 INYENTOR.

udolph Leonard Hascbe April 1, 1941.

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MANUFACTURE OF ACETYLENE Filed July 1.0, 1937 2 Sheets-Sheet 2 FIGZ. FIG.4.

102 FIG .5.

I400 FIG. 6.

Hf 1 T HEUIREZI? FOR IEED I I I I I200 BA ICE BUTA E AT D N 8-! I I I II000 I I I 800 1 L TE Q: 600 F! E "M a:

W. It 200 L PER 23? 400 600 800 /000 1200 /400 BIU. REQUIRED TUBETREVERSED Z0 40 Rudolph Leonard Hasche Patented Apr. 1, 1941 7 2,236,535I MANUFACTURE OF ACETYLENE Rudolph Leonard Has che, Kingsport, Tenn, as

signor,

by 'mesne assignments, to Wulfl Process Company, Los Angeles, Calif., acorporation of California (I i Application July 10, 1937, Serial No.153,044 9 Claims. (Cl. 260-679) This invention relates to a process ofmaking acetylene, or a gas containing acetylene, together with numerousby-products to be named and characterized herein. More particularly itrelates to a pyrolysis process for making acetylene more economicallythan has heretofore been known.

, Various processes for the manufacture of acetylene are shown in theseveral Wulfi patents, for example, 1,880,308 and 1,880,309. My processis similar to the processes described in the Wulif patents in a numberof respects. However, my process constitutes an improvement thereover aswill be apparent as the description proceeds.

This invention has for one object to provide a "method of producingmaximum yields of acetylene from each unit of raw hydrocarbon to beprocessed. Still another object is to provide a pyrolysis process whichpermits the use of a' variety of proportions of diluent. A' stillfurther Object-is to provide a pyrolysis process in which there is aspecial preheating before final pyrolysis, thus producing improvedperformance and increased capacity. A still further object is to providea high temperature pyrolysis process in which there is a definiterelationship between the heating surfaces and volume heated. A stillfurther object is to provide a high temperature pyrolysis process inwhich there is definite expansion ratio between the materials pyrolyzedand the products obtained.

Still another object is to provide a pyrolysis process in which theremay be reuse of a chosen part of the products which have been previouslyformed therein. Another object is to provide a high temperature processfor the production of acetylenic hydrocarbons from raw materials whichmay contain more or less sulphur components. A still further object isto provide a process for producing acetylenic and oleflnic hydrocarbonsin equipment which may be comprised in part of nickel. Other objectswill appear hereinafter.

I have found from extensive investigation of a number of factors ofoperation, wherein increased economy of operation and other advantagesmay be obtained. As indicated above, the several Wulif patents discloseprocesses of acetylene manufacture. These patents set forth variousdetails such as a number of different type hydrocarbons that may beconverted to acetylene, a number of difierent diluents that may beemployed, temperatures, pressures, details relative to rapid cooling anda number of other factors. These patents also show suitable apparatus.

Since these and other details are already available, it appearsunnecessary herein to repeat such information, hence, on certainfeatures discussed herein only brief references are made. While anysuitable apparatus may be employed for carrying out my invention,certain apparatus shown in the Wulif patents being satisfactory, Ipreferto employ an-apparatus arrangement as shown herein.

For a more complete understanding of my invention, reference is made tothe attached drawings in which Fig. l is a. diagrammatic representationin the nature of a flow sheet of one apparatus set-up for carrying outmy invention. Figs. 2 and 4 are side elevation views of fillers orcorebusters which may be contained in my pyrolysis tube. Figs. 3 and 5are end views respectively, of aforementioned corebusters. Fig. 6 is achart showing a heating relationship, with particular reference to mypreheating ste In Fig. 1, the primary stock to be used in makingacetylene and other products, is supplied from the container I. In theline 2 may be a valve 3 for regulating the rate of ,flow. Followingvalve 3 is a flow meter 4, followed in turn by a heater 5. The heater 5may operate in the conventional manner by admitting at l a heatingmedium about the tube 6. At the pipe juncture ii the primary stock joinswith diluent furnished through the pipe l2. Valve it serves to adjustthe rate of now of the diluent, and i4 is a flow meter in the line. Thepipe may also make communication with the point of juncture H foradmitting secondary stock in a manner to be described.

Pipe l5 carries the feed to the preheater It;

This preheater comprises a housing 38 and a heating coil i! thatreceives the feed from pipe IS. The heating medium for the feed in coilI! may be flue gas in countercurrent, coming from the cracking furnace42 operating in conjunction. Flue gases forming in the combustionchamber 83 of the said furnace, pass into a duct 65, and may bemanipulated such as by the two dampers 3| and 40, to serve as mean forcontrolling the degree of preheat in coil I1. From the coil l'l the feedpasses into the pipe IS, in which there may be a chamber as at 86.Integral therewith may be a thermocouple well 61, where the degree ofpreheat of the feed may be determined by the thermocouple 8| indicatingat the pyrometer 82. If a chamber is not desired, then the thermocouplewell may be integral with the pipe l9 which leads directly to the trap20. .The purpose of this trap is to catch any oils and tars that formfrom the feed at times due to the action of the tailed descriptionappears unnecessary.

preheater it. Any accumulation in trap 2G may be drained at will throughvalve 2!,

The preheater is connected through pipe 22, to

the cracking tube 2% through a fitting 23. The cracking tube 24 may beheated by one or more burners as at 25, supplied with fuel and airrespectively through valves 26 and 21. Preferably there are at least twosuch burners, disposed to give the most uniform possible heating of thesaid tube. Cracked mixture leaves the tube 2%, passes through a fitting29, and enters pipes ill), M, and 15 which convey it to the quencherd3,which it enters at a point 32. The said pipes 30, id and 15 arepreferably water-jacketed or otherwise cooled, while in fact bothfittings 23 and 29 are of cooleddesign, for purposes to be brought outin full later. 79 indicates a point of entry for a thermocouple "it usedfor testing at different levels within the tube 2d, temperaturesindicated on the pyrometer ll.

While I have indicated the use of temperaturemeasuring instruments; flowmeters and the like, at Various points in my apparatus, it is to beunderstood that my invention is not limited to such construction or useof such instruments and various :other instruments may be employed orattached to my apparatus at difierent points.

The quencher it is preferably a tower fitted with liquid connectionssuch as 3%, 35, and 33, each of these having a valve as indicated foradjustment, and a spray device 66 within the tower in operating relationto the said liquid connection and valve. The cracked mixture, cooled bythe pipe 30, on entering tower 13, at 32, is suddenly chilled by thewater or other liquid sprays within, to a temperature at which acetyleneand ethylene are stable. At the same time the diluent, if of boilingpoint substantially higher than that of the final gas temperature in thetower, will for the most part be condensed. Together with such diluent,will be removed from the cracked mixture, the greater part of any oiland asphalt or tar vapors, particles of solid organic matter, andparticles of carbon that the said mixture contains as a result of thecracking operation in tube 2d. Such material removed from the gas, forthe most part is liquid, making possible its removal from the tower atwill, through the trap 6 5.

At a point 33, the unit 53 is connected to filters 3i, 3? and oilscrubber 86. The oil scrubber 88 is connected to the suction end of thepump w, whose full function is to be explained later. it is a valve forby-passing part of the discharge of pump-B9. The said valve H isoperated by pressures in chambers 23 and 63 communicating through pipesi2 and i3, respectively. The purpose of this valve ii is to maintain adesired ratio between the pressures in the chambers 23 and 83. The exitend of the pump 69, is connected to a meter 6, a gas holder 85, and thenpreferably to a dryer 65.

It should be repeated that Fig. 1 does not show each of the units of theprocess in its exact form, but diagrammatically. More particularly isthis true of unit 48. The unit 38 is interconnected with the system atpoints M and 55. These units may be in the nature of scrubbing towers,extractors or other construction employed in the art for recovering andseparating acetylene and ethylene. Inasmuch as a number of constructionsfor recovering and separating acetylene and ethylene are shown in theart, further de- It is to be noted in passing, however, that somearrangement may be employed wherein medium employed in unit 68 may beconducted thereupon and fed to parts 33, 85, and 36 through conduit 9!.The stripped gas may be removed as at 62.

In any event the acetylene produced in my process may be separated as at68 or reacted, and the ethylene or other olefine produced likewiseseparated and conducted to conduit 53.

Figs. 2-5 show construction which may be contained in my pyrolysis tube2%. This construction serves to improve the pyrolysis process byfacilitating heat transfer as Well as (in cooperation with tube 24) ofproducing a definite area ratio within the pyrolysis chamber.Construction may be of a number of types, for example, one type ofcorebuster may comprise a cylindrical refractory unit mi. This unit willhave positioned on it at various points, lugs me which serves to more orless center the corebuster within the device. Channel 503 is for thereception of a pyrometer unit or other mechanism. If desired, aconstruction such as shown in Figs. 4 and 5 may be employed. Thisconstruction includes a refractory unit W6 having thereon theprotrusions lfl'l which serve to position the corebuster within thepyrolysis tube. In general, this modification is more or less of astar-shaped design and as already pointed out, may contain a passagewayHill for the reception of temperature-recording instruments.

The operation of my process with variations, is preferably carried outin the following manner, reference being had to the accompanyingdrawings, principally Fig. 1. The various mechanism in my apparatuswould be set in operation. Thatv is, fuel and air pressure would besupplied to the burners, filter material, oil scrubbing medium andcooling medium would be supplied to the various parts. The pyrolysistube and preheater would be heated. The various spray valves 36, 35 and36 are open while quenching agent flows out through trap M. The valve 1!would be adjusted so that the pressure exterior of pyrolysis unit 26would be about equal to the pressure in the interior thereof (or at someother predetermined relationship) for minimizing leakage or controllingor inducing leakage in a particular direction. Steam or other diluentmaterial, such as shown in the Wulff patents, may be allowed to proceedfrom the valve it. When the ap paratus has obtained the desiredtemperature, material to be pyrolysed may beied in from container 1through the various conduits. Heat may be applied at 6 if desired, forvaporizing the material which is to be pyrolysed. The proper proportionsof materials, of course, may be obtained by regulation of the valves andnotation of the flow through the respective meters. Any materialscondensed in the preheater may be removed from trap 28 through valve 2i.

I prefer to operate at a high temperature of preheat within a particularrange, and dampers 3| and id are accordingly adjusted to this end. Myhigh temperature of preheat is desirable. since I have found that if thetemperature in metallic tubes, such as the coil H, is properly appliedthe greater can be the per hour capacity of the pyrolysing tube 24,which may not so easily pass heat as a metallic tube, and which also ismore expensive and less durable. In short, while .my process formsacetylene at so high a temperature as usually to require a refractorytube in the final treatment, still much of the load of heating can betaken off the said tube through the use of the proper preheat in lessexpensive equipment. Further than that, I find that the changes thatoccur in the feed as a result of the preheating, can be very beneficialif. they are controlled. In other words, certain reactions possible inthe feed during preheat are useful, and others are not. It is thereforea part of my invention to single out such reactions as are useful, andpermit them to occur alone or predominately during preheating of thefeed, and to such an extent as conduces to the economy of my process.

Reference is now made to Fig. 6 which is a graph that illustrates one ofthe advantages of my method of preheating. The curve gives. the B. t. u.value required to heat one cubic foot of butane diluted with eight cubicfeet of steam. Up to 600 C., the curve is steep, since the only need ofheat is due to specific heat. From above 600 C. the curve is much lesssteep, due to considerable demand for endothermic heat. I have found,therefore, that to preheat at above 775 to 800 C., namely, above thepoint where endothermic heat is required, materially alleviates the loadon the pyrolysing step. Attention is called to the fact that the curveshown in Fig. 6 represents butane at a steam dilution of eight volumesper volume of butane. In my process, I may dilute with as little as 3volumes of steam to l of butane. In such cases, it is evident that theendothermic heat is then a much larger proportion of the total heatrequired by the feed in the preheater. Thus it becomes part of myinvention to preheat above 750 C. and generally above 800 C.

For a still further understanding of my preheating step, reference ismade to the following table showing a series of tests carried out withnormal butane at a dilution of eight in a tube of about .546 inchinternal diameter, containing a corebuster of .375 inch outsidediameter. The rate of flow of steam used as diluent was .222 and therate of fiowof butane was .208 c. f. m. The time of passage was, ofcourse, extremely rapid and the residence period of the materials in thetube was substantially less than 116 of a second.

Percent by weight of N-butane converted to various products Theaforementioned table shows plainly that from the standpoint of economyof raw material ordinarily 1000 C. is a better temperature than lower orhigher temperatures, since the total of olefines is at a maximum there.Attention is called however, to the larger proportion of butaneconverted to carbon monoxide at higher temperatures, which no doubtaccounts for the disappearance of some olefines.

Care is taken herewith to point out that the term expansion in the,aforementioned table is applied to fixed gas in the feed; afterpreheating rather than to cracked gas as above defined.

The results in the aforementioned table show that different temperaturesmay be employed .to secure somewhat different decomposition products.One may work to a maximum volume concentration of oleflne plus acetyleneor to a maximum percent by weight conversion of raw materials itoolefine. It is to be understood that the 1000 C. which I desecribe asthe optimumtemperature of preheat is not altogether inflexible but, ofcourse, depends upon factors such as the particular raw material used,the length of time that the feed is subjected to preheating, and thetemperature of preheat. In general, for longer periods of preheating,the temperature should be lower than 1000 C. whereas for a short periodthe temperature might be somewhat higher. all instances, however, thetime of preheating is preferred to be kept to a low value, under a fewseconds, preferably considerably under one second. The upper limit ofthe temperature of preheat is conditioned, however, largely by thedisappearance of olefines due to carbon monoxide in excessive amounts.In other words, I do not wish to preheat at such a high temperature orfor such a long period that materials being preheated or formed duringmy preheating would become converted to carbon monoxide or'othernon-useful components. When I have reached the temperature in thepreheating wherein the olefine component is disappearing, due to theformation of carbon monoxide, I conducted the preheated materials to the.tube 24 of Fig, 1. In this tube high temperatures may be employed,while yet controlling the quantity of carbon monoin'de formed. This isdue to the selection of materials such as carborundum or otherrefracrtory to .the cracking tube wall, combined with a brief period ofresidence in the same tube.

Therefore, the feed, thus preheated in the coil i1, and whether or notmodified in chemical con stitution thereby, proceeds then to the fitting23, which is now already hot and does not condense diluent. From thereit courses through the cracking tube 24 where is formed a substantialamount of acetylene.

- Feed having been cracked in the tube 24, then becomes a mixture ofcracked primary stock and diluent, including by-products of suchcracking as for instance organic condensation products and carbon.Included in the said mixture are any products of reaction of diluentwith the primary stock or with any of the products it forms in the tube24. This mixture of gas as described in .the present paragraph has beentermed cracked mixture, and will so be called herein. And while themixture is given this name, it is nevertheless to be understood thatthere will be a certain amount of physical and chemical change in themixture between the point that it leaves the tube 24 and enters thequencher 43 which fixes its composition. The said path is waterjacketedor otherwise cooled (as with refrigerants) to chill the cracked mixtureas rapidly as possible from the instant of exit from the tube 24. Tothis end even the fitting 29 may be Waterjacketed. I therefore drop thetemperature of [the cracked mixture instantly to any predetermined pointmore or less in accordance with the teaching of the Wulfl patentsaforementioned.

' The products treated in unit 43 are clarified, cooled and purified tosome extent. However, the filters 31 and scrubber 86 remove carbonparticles, oils and any other materials contaminating the crackedproducts.

After leaving .the scrubber 86, the cracked gas is picked up by pump 69.The adjustment oi the stud 16 on .the by-.pass valve H is now made so asto hold about the same pressure within chamber 23 as within thecombustion zone 83. Valve H of course performs this function by varyingsuction on the pump 69 through the bypass line in which it operates.Higher or lower pressure may also be produced.

After the pyrolysis has continued for a short period recirculation maybe set up. To this end are opened valves 83, 62, 51, and 6t, and thepump 84 is set in operation. "Then valve 80 is manipulated to forcecracked gas into the gas holder 85, and adjusted so as to hold the gasholder always partly full. Then valve 8 is opened .to cause a flow ofgases through the unit or units designated at $8 and valve 8b is againadjusted to maintain a quantity of gas in the gas holder 85. Valve 6% isthen further opened, increasing the flow' of gases in til. Theseoperations with valves 5d and 80 are repeated rtill at last valve 8!) isclosed, and valve M is open at a point that will still hold a quantityof gas in the gas holder 85. According to the actual manner of operationof 48, these are set in action and adjusted till satisfactory resultsare evident from .the purity of ethylene and acetylene isuing.

thereupon and from the. leanness of stripped gas issuing from the valve62. At this point I may recirculate ethylene by opening valve 9 so itwill mix with diluent and primary stock from container l as beforedescribed. As valve his then 0 admitting ethylene (or other secondarystock) to the system for recirculation, valve 65 is adjusted to relieveonly what ethylene is not passed through the said valve 9, for otherwisethe process of separation may be disturbed, or the purity of .theethylene may drop. And if all the ethylene produced is recirculated inthis manner, then obviously valve 6t should be closed. It will also beobvious from Fig. 1 that the pump 85 of need would have a deliverypressure convenient to the niceties of control as to recirculation andsufficient to exceed easily the pressure in the pipe juncture H wherethe mixing is to take place.

In the material immediately foregoing, the separation of acetylene fromthe cracked gas is described as carried out in a unit or unitsdesignated 38. And it is herewith repeated that the system of separationis only illustrative. Any

of a number of methods may be employed. The

separated product may well include more or less of the material to befound in my cracked gas. Hence, in the following matter reference willbe had largely to secondary stock rather than ethylene as secondarystock.

Such diluent as may have been of boiling point too low to be condensedin the quencher 13, will pass out of the separation system still in thestripped gas leaving the point 62 of the tower d3. According to the typeof diluent, it may be removed from the said stripped gas in ways knownto the art, either for increasing the value of the stripped gas, or forrecovery of the diluent as in repeated use. If the stripped gas alsocontains acetylene at the said point of exit 62 of the tower d8, ofcourse that tools recovered for use as may be desired. Thestrlpped gasresulting may very well be used as fuel for firing the cracking furnacet2, as I elect to do, for reasons to be pointed out hereinafter.

When recirculating ethylene, or olefins generally, I may secure a highercontent of acetylene in the resulting gas than before, as well as ahigher yield. Also, I may have a higher content of ethylene, due to thefact that ethylene survives the heat treatment in the cracking tube oftemperature herein. v

steam used for dilution, are all measured inassesses standard cubicfeet, and ratesof flow in cubic feet per minute, for convenienceabbreviated c. f. and c. i. m. So for all primary and secondary stockand any diluent herein, a standard cubic foot of gas represents thequantity of gas in such a volume at 25 C. and one atmosphere absolutepressure, and will so be understood herein. The weight of such a volumeof a given gas or gas mixture, is assumed to be equal to the molecularweight; or average molecular weight, in pounds, divided by 384. Andwhile steam is of course non-existent in those conditions, still thehypc= thetical volume is herein computed by extrapolation as though itdid exist, and behaved like a fixed gas such as nitrogen. In order toestablhh without possible doubt the meaning of one standard cubic footof steam, it will be assumed herein that such a unit of steam weighs18/384=0.0d68 pound avoirdupois, arrived at exactly as for gases. Thesame formula is herein to be applied to other diluents and othernormally liquid substances according to their molecular weights. Thecare'exercised in this paragraph in establishing units and factors ofconversion is for eliminating any possible confusion, and to the factthat for purposes of test ing variables relating to my process, 'it isbetter to speak in terms of volumes rather than weights, while forpurposes of elucidating economies, the converse practice is moreconvenient.

The item Dil." signifies dilution or extent of dilution, expressed asthe ratio of rate of flow of diluent to that of stock being cracked,each expressed in c. f. m. The itemFExp." signifies expansion or thenumber of cubic feet of cracked gas formed with one cubic foot of stockcracked. Gas analysis is given in percent by volume. Conventionsdeveloped in this paragraph will be used throughout herein, except thatExp." in preheater tests may at times refer to fixed gas resulting frompreheating rather than to cracked gas, as will be clear in context.

Ratio of surface to volume will be expressed in square feet per cubicfoot. For instance, in a preheater tube of 1.75 inches internaldiameter, without corebuster, the said ratio is If a corebuster ispresent, the sum of the internal areas exposed to the stream, is dividedby the net volume bounded by said areas. If the corebuster iscylindrical, the volume is then annular. If the outer surface of thecorebuster has a special shape, the area of that surface is estimatedfor use as above.

Ratio of area to volume, hereinafter to be termed area ratio, in thepreheater tube may range from as much as 250 to as little as 5. if havefound that the range permissible here is very wide, since it may becompensated not only with temperature, but also with residence period.For the higher the area ratio, the more rapidly the gas will absorbheat, and the less severe the temperature needbe, or the less the period7 2,286,535 of heating. Wide fluctuation of area ratio brings widefluctuation of residence period, but not such -a great variationoftemperature. Hence, the

temperature range remains nevertheless rather well fixed. All. the more.however, is the emphasis'oi' gauging extent of preheat by the expansionas above defined out in more detail.

Dilution has little influence ,on results that may be secured inpreheating, so long as the preheater is designed to take care of theheat transfer requirements that arise. Dilution will thus be kept fordiscussion under the cracking stage.

In addition to preheating as described above, and thereby obtainingimproved yields, I have found several other features which may beapplied in my process for the manufacture of acetylene withthe resultantproduction of still further improved yields. I t-is understood, however,that these various steps to be described, while preferred, are to someextent optional. Hence, one or more or a combination of the fol-=-lowingfeatures may be utilized.

I have found that if the feed materials, such as my primary or secondarystock, contain appreciable portions of sulphur in the form of hydrogensulphide or other volatile sulphur compounds such as light mercaptans ororganic sulphides, the yield of acetylene as well as ethylene or otherolefines is diminished thereby. For further illustrating this point,reference is made to Tables 1, 2 and 3. In Table 1 is shown acomposition of a gas containing hydrogen sulphide. It is, of course,understood that this is illustrative and gases encountered might containmore or less volatil sulphur materials.

TABLE 1 'Firom-a comparison of Tables 2 and 3, it will beobserved thataggregate yields of acetylene and olefines may be considerably improvedif sulphur is absent. In the example of Table 3 the hydrogen sulphidewas removed from the gas by treat ment with a caustic soda solution in aconventional manner. Cracking was carried out in the equipment alreadydescribed. It is also evident firom Tables 2 and 3 that .there isgreater expansion due to the presence of sulphur. Further computationswill show that the additional carbon monoxide formed, due to thepresence of suland'as will be pointed phur, may probably be accountedfor by the decrease in acetylene and ethylene.

Therefore. the net result of the presence of sulphur and particularlytoo great a content of sulphur in the materials to be pyrolyzed', is toreduce yields. It is therefore a pant of my invention to provide againstthis difficulty, inasmuch as a great amount of raw material (such as thecomposition shown in Table 1) is available for use in my process. It is,of course, possible, as already indicated, to remove sulphur from thestock before subjecting it .to treatment. There are a number ofprocesses known for removing sulphur and I may apply any one of theseprocesses to my stock before conducting it through the apparatus.

I have also found that it is possible to use such a stock which containssulphur by substituting or complementing [the treatment for removingsulphur, with a partial or total substitution of any steam diluentssupplied to the feed. Another more nearly inert diluent or a suitableequivalent of re duced pressure or both of these expedients may beemployed. I have discovered that sulphur in conjunction with steam is afactor tending to destroy .the acetylene and ethylene which I wish toproduce. Hence, I disclose the utility of operating with less sulphur,or if sulphur is present, less steam in the presence thereof or withless of each. In closing this point, it is desired to bring out thatthis feature has considerable utility because of the availability oflarge quantities of sulphur-containing gases which may be treated by myprocess.

Referring again to the preheater construction, it is preferred to useany of the various heatresisting alloy steels such as chromium steels,chrome aluminum, chrome molybdenum or chrome tungsten steels. However,there ace various other heart-resisting alloys such as chrome nickelalloys, chrome nickel steels and the like. In operating my process insom instances such as with previously constructed apparatus, theoccasion may arise wherein the preheater tubes are constructed ofmaterials containing more or less nickel. I have found in such instancesthat improved operation may be obtained by using less steam as adiluent, substituting therefor, a more nearly inert diluent if not alsoa certain measure of reduced pressure. Under some conditions I may alsoelect to use preheater apparatus containing a moderate content of nickeltogether with less steam and an inert diluent or a measure of reducedpressure. I may also counteract undesired reactions by introducing intothe feed a substantial part of any steam diluent, or other diluent whichmay with a particular preheater or feed produce difficulties,immediately after the preheat rather than as above described.

From the preceding it is apparent that I have set forth a process whichmay be applied not only to high-grade stock, but also to less desirablestock which may contain splphur. It is also apparent that I haveprovided a process which may be operated in apparatus constructed of anyof the various metals and alloys usually ncountered in the industry.

With further reference to my novel preheating step the exact temperatureof preheat in a suit-able tube and with a suitable diluent, already hasbeen stated to depend to some extent on the period of heating employed.It should also be made clear that this temperature is dependent also onthe nature of the raw material used, being toward the higher values forraw materials of lower molecular weight. It the temperature is to be.the same, then the period of heating should be somewhat longer with rawmaterials-oi lower molecular weight. In general, I prefer also to useslightly less dilution with raw materials of low molecular weight,excepting in the case of methane. For, in the case of methane, I havefound that with a preheating temperature of from about 900 C. to 1100"C. and a period of heating suited to whether a higher or lowertemperature is chmen, there can be secured under sufllcient dilution,particularly with steam, a considerable conversion of methane by thepreheating step. Such a change in the preheating step probablyconstitutes an actual synthesis requiring the union 01! two molecules ofmethane or rather of their two ca-nbon atoms. This is of considerablimportance in the formation of acetylene, inasmuch as it will be notedthat acetylene is a two-carbon atom molecule, whereas methane has but asingle carbon atom. By being able to convert apart of the methane to aheavier molecule by means of my preheating step, it is apparent that theformation of acetylene therefrom in the cracking step is alsofacilitated.

I prefer to preheat longer and use higher dilutions with methane thanwith other raw materials. However, I prefer the same approximate finaltemperature of preheat (namely, around 1000 C.) in order that the endproducts in every case may be similar. The period of residence in thepreheater should be the same as with my other raw materials. That is tosay, when acetylene' begins to appear in my preheater on feed containingmethane as a raw material, I would elect to speed the feed through itsfinal stages in the same manner as has been described in reference tobutane and other raw materials.

Having referred specifically to the case of methane as against other rawmaterials in the operation of my process, I may elect to make use ofreaction chamber 66 in the line it (see Fig. 1). This reaction chamberwould receive feed that has already reached the temperature at whichmethane or other materials are becoming converted to heavy moleculessuch as the olefines, and holding it until all such olefines haveformed. The period of time, of course, would be dependent upon theinternal volume of the reaction chamber in comparison to the rate offlow of feed. It is understood, however, that the chamber is placed inthe preheater coil at a point preceding that at which acetylene forms,for it is the purpose of said reaction chamber to give time, forexample, for ethylene to form, whereas for forming acetylene no largetime element is necessary.

It bears emphasizing that those skilled in the art will agree as to thedifiiculties presented when attempting to determine true gastemperatures for purposes such as relate to my process. I emphasizealso, therefore, that when I report, discuss, or choose temperatures,these are measured and chosen for what they may actually be, and notnecessarily as being exactly what they were intended or hoped to be. Butbeing temperatures measured in a definite specified manner, thoseskilled can duplicate experiments on the basis of such guidance, andsecure similar results to those I report herein.

Thus for these and other reasons given, it is not possible to determinewith finality the actual length of time of heating of a gas in stream.Past statements in the literature relating to the said period of heatinghave, however, been particularly nebulous arbitrary, hence, I propose toestimate them only on the basis of iully detailed specifications ofexperiments, and fully clarified of elements of error and uncertainty.

Hereinafter the said period of heating will be termed residence period,and will be understood to be the length of time in seconds that a givenportion of gas, whether in stream or static, is undergoing a particularunit heat treatment, re-

mains in the unit giving that treatment. For

instance, the residence period for feed bein D heated in the preheater16 of Fig. 1, is that number of seconds during which an element of thefeed remains inthe coil H or the coil I'I plus the reaction chamber 66as the case may be.

If preheatingof the feed is carried out without a reaction chamber suchas may be desired for methane, the temperature rise of the feed duringits passage through the preheater tube will be nearly proportional tothe length of tube traversed, particularly if heating is uniformlycountercurrent as is common practice. The graph in Fig. 6, however,shows how the feed temperature suffers retarding in this respect, toward600 C. due to the endothermic heat requirement discussed.

In general, the feed enters the preheater at about 100 C. and oneatmosphere absolute pressure, that is, zero gauge pressure. At times, Imay wish to use higher temperatures and pressures, as for instance if Iwish to speed the feed through the preheater, or again if I desire tomaintain an appreciable gauge pressure at the inlet end of the crackingtube. Indeed, it is my practice to hold a few pounds of gauge pressureat the inlet to the preheater tube, in order to hold the feed in flowand still hold zero gauge pressure at the inlet to the cracking tube. Itwill 'be assumed, however, for practical purposes, that the feed entersthe preheater tube at 100 C. Since also I may preheat up to 1000 (3.,the graph of Fig. 6 has been constructed to represent this rise intemperature along the length of preheater tube, in which the feed hasresidence. Though it is clear that the temperature is not strictly astraight-line function of the distance passed, such will nevertheless beassumed.

Thus, if there were only the natural thermal gaseous expansion of thefeed in traversing the preheater tube, as there would be with a gas suchas nitrogen, similarly passing through, one would arrive at theresidence period by considering the internal volume of the said tube inrealtion to rate of flow and average temperature, say at zero gaugepressure. This I propose to do, neglecting the unavoidable expansion dueto chemical dc composition of the raw material. For the pertinence of acorrection due to this factor is very doubtful in view of the questionas to the temperature distribution of such expansion. I recognizefurther that this error is not constant, but dependent on the extent ofexpansion, as well as on the dilution. For with less dilution the rawmaterial occupies a larger proportion of the total feed volume, andtherefore the expansion causes a greater error in estimation ofresidence period.

Thus simplified, the method oi? computation may be illustrated to removeall doubt of proce dure and definition. With 12 c. i. m. of butane and96 c. f. m. of steam as diluent, the total rate of flow is 108 c. f. m.If the temperature of the preheater on the average is an average between100 and 1000 0., then the average rate of flow effectualis .r' gg gg103:304 cubic feet per mimlte of thermally expanded feed. Then if thepreheater tube volume is 2.66 c. 1., the time of heating will be r 3040.00870 minute or 0.5 second, in which more than one significant figureis not Justified due to uncertainties and simplifications. e

Having now covered substantially my disclosures on preheating as a stepin my process, I proceed to give the operating and preferred ranges ofvalues of variables that determine the results of preheating.

I prefer to preheat as high above 800 C. as possible, being limitedlargely by excessive formation of carbon monoxide, which as has beenshown, is a variable factor. With good equipment in conjunction withexpedients of operation herein set forth, I prefer to carry preheat upto 950 C. and beyond when possible, to include some acetylene formationif possible. As a general thing, however, I prefer to preheat from 850to 900 C., realizing that the actual temperature which is best to use,depends on the residence period, and on practical limitations such asheat-resistance of alloys available for construction of preheater.

Residence period may well range between 0.1

and 4.0 seconds, for raw materials except methane, and may convenientlybe 0.3 to 0.8 second for ordinary operation. Residence period withmethane as raw material, may be from 1.0 to 5.0 seconds, depending oncertain considerations, as

for example the conjunctional use of reduced pressure. The two sets ofranges here given of course are interrelated with the range oftemperatures of the preceding paragraph. It will be seen that a slightalterationof temperature permits a rather wide variation of residenceperiod.

Since temperature and residence period are so related and notindependent, I prefer to introduce a third measure of extent oftreatment, which is more directly indicative of whether the feed hasreceived the proper thermal treatment. I find it strongly advisable tobe guided, in preheating, by the expansion that results, that is, by theafore-defined ratio of volume of fixed gas formed to volume of rawmaterial that forms it.

For either normal or isobutane, or for a mixture of them, I prefer topreheat until I have secured an expansion of from 2.0 to 3.5 wherein Iallow for a reasonable amount of expansion due to car bon monoxide andwater-gas hydrogen. Correcting for carbon monoxide, the range of exapansion would be 2.0 to 3.2, while it may be said in general that 2.5expansion is approximately the best in view of present-day limitationsas to non-catalytic metals. And it is not be forgotten that rawmaterials of lighter molecular weight in turn have their owncharacteristic expansions by which I elect to judge optimum extent ofpreheat, while for the light olefines it is again slightly different.Thus for methane I prefer expansions of 1.1 to 1.4:, including smallamounts of carbon monoxide, say of not over 5% by volume in the fixedgas. Expansion for ethane should be from 1.4 to 1.8, while that ofpropane should be 1.8 to 2.2. No expansion is required of ethylene,except for small amounts of acetylene formed, since it is of courseitself a suitable raw material for the cracking operation. Expansion forpropylene should be 1.5 to 1.9, and for butylene 1.8 to 2.2. Thesefigures I use as a basis for determining the most advantageous expansionof raw material according to its chemconductivity and resistance tospalling may be used as wall material for my cracking tubes, I havepreferred carborundum. The corebuster within the tube canbe mad-e ofeither of these materials, or of still others such as mullite, since thecorebuster is not subject to quite such severe strains as the tube, andneed not remain in such superior mechanical condition. Whatever thematerial of the corebuster, it must be such as not to slag down with thetube material. For atmospheric pressure work I prefer carborundum,although other materials are suitable.

While in carrynig out my process the tube shown in Fig. 1 at 24 may beof any suitable size,

r the purposes of illustration I describe my process as being carriedout in a 4-inch internal diameter tube of about inch wall thickness.This tube may contain a cylindrical corebuster about 3 inches indiameter, thereby giving an area ratio of 96. If in place of using thecylindrical corebuster I should employ corebusters of the type shown inFigs. 4 and 5, I would be able to increase the area ratio to 200 andabove.

If I assume for consideration of operating variables, a 4-inch tube of 7inch wall thickness and a 6-foot length exposed to heating in thecombustion chamber with a 3 inch cylindrical corebuster giving constantgas path section and a feed of butane and steam at a dilution of 8, Ican more specifically illustrate my process. The feed would enter thecracking tube at about 900 C., preheat and at a preheater expansion of2.5. It is understood that these, values are set forth merely for thepurposes of illustrating my preferred embodiment and as apparent fromdisclosure herein, ma be varied and modified.

I find that for securing the optimum production in my process thereshould be obtained an expansion of from about 3 to 4.2 in the crackingtube. For further illustrating what has been said with respect'toexpansion, reference is made to Table 4:

TABLE 4 Relation of butane expansion to yield Yield, vols. per 100 vols.

(1H4 Total While I have discovered that my process operatessatisfactorily with dilutions as low as 3, such low dilution is notpreferred, excepting in instances aforementioned, where the feedcontains volatile sulphur or the preheater is constructed of certainmetals, because such lower dilutions give more rapid accumulation of tarwhile providing excess -i'uel for the furnace. Hence, I

prefer and have found that dilutions from about to 8 and at times up to18 when using a raw material containing only a small proportion ofethylene, are particularly satisfactory. As iridicated in the precedingdisclosure, with respect to methane my process may be carried 'out inone of two directions. Either I convert in the preheater at dilutionsfrom 20-40 thereby obtaining ethylene from the methane, after which thepreheated feed is handled as ethylene-rich feed. Or, when treatingmethane I may use dilutions from about 3-6 together with a crackingtemperature from 1300 C. to 1600 C. With respect to ethylene feed,preferably this should have expansion of about 1.7 to 2 ormore, while atemperature range 0! from 1150 to 1400 C. would be suitable. Methaneshould have an expansion of from about 1.4

to 2.2, while the temperatures required in the pyrolysis tube 20 wouldbe higher than for other materials, namely, above 1300 C. and up toabout l600 C.

In the preceding, I have illustrated my process in some detail withrespect to butane as raw material as well as methane. There are,however, a number of other raw materials which can be treated within thesame temperature range and under similar conditions. For approximatelybest operation from each of these, the range of expansion should be; forpropane, 2.0 to 3.6, preferably 3.0; for ethane, 2.1 to 2.9, preferably2.5; for methane, 1.6 to 2.2, preferably 1.9. For the olefines,expansions would be set slightly lower than the corresponding parafilns.

For mixtures of any of the materials herewith listed, expansion shouldbe computed as though each component expanded alone according to thefigures above given. Thus, an arithmetic average that takes intoconsideration the volumetric analysis of the raw material mixture, willgive the favored range of expansion.

With further reference to conditions prevailing in my cracking tube 20,I assume that the temperature of the preheated feed to the crack.- ingtube is at least about 900 C. I assume a temperature rise in thecracking tube of, for example, from- 900 C. to preferably around 1350"C. or an. arithmetical average temperature of about 1125 C. For thistemperature it my be I stated that the residence period for the 4-inchtube under consideration may lie between 0.12 and 0.002 second, and inmany instances these limits may be further narrowed to 0.02 to 0.004second.

As already indicated to some extent, the rate of reaction for methane issomewhat slower than for other materials. Hence, lower rates oi flow maybe used, excepting when considerably high temperatures are employed.However, residence periods with respect to methane are within the limitsaforementioned. It may be further mentioned that when employing methane,dilutions toward the lower limit are preferred. In general it may besaid that the residence period (time interval) may be between about 0.01to 0.004 second. My reaction is generally conducted at space velocitiesin excess of 100,000 and in many instances in excess of 200,000.

While I have illustrated the use of a 4-inch tube, it is to beunderstood that my invention is not restricted to such construction. Imay employ larger or smaller tubes having thicker or thinner walls. Imay also elect to use a specially adapted metal or other metal alloy inrelatively thin gauge, which would be coated externally or internally orboth with a vitreous enamel of high softening point. In lieu of enamelexternally there might be formed an adherent oxide face. In place ofenamel there might be employed the carbidizing of one or more of theelements in the metal walls.

From Fig. 1 it may be seen that the acetylene, ethylene andotherproducts which may be produced by my process such as benzol, toluene,xylene, naphthalene are separated at various points. 'The naphthaleneand the like may be taken out in the filters. I find that the residualgases leaving the unit 00 at 62 may be comprised of 50% or more hydrogenand as such, form an exceptionally good fuel for my process. Hence, asaforementioned, this fuel may be fed to burner It is therefore apparentfrom the preceding that my invention is suspectible of modification.Hence, I do not wish to be restricted, excepting insofar as isnecessitated by the prior art and the spirit of the appended claims.

What I claim and desire to secure by Letters Patent of the United Statesis:

I. A method for the manufacture of unsaturated hydrocarbons includingacetylene from feed materials essentially comprised of nonacetylenichydrocarbons suitable for decomposition into acetylene and olefines,which comprises preheating said feed materials to temperatures in excessof 750 C. for a period of time less than 5 seconds, sufiicient to formsome acetylene in the preheated feed, but insufilcient to cause theformation of substantial quantities of carbon monoxide therein,substantially immediately subjecting the feed in its preheated conditionto further heating at temperatures between 1150 0-1450" C. for a periodof time less than onetenth of a second for forming substantial yields ofacetylene and oleflnes, rapidly cooling the acetylene materials whichhave been formed, separating and recycling to the feed at least a partof said oleflnes.

2. A process for the manufacture of acetylene, which comprises obtaininghydrocarbon material essentially composed of non-acetylenic hydrocarbonssuitable for decomposition into acetylene and ole-fines, diluting thehydrocarbon material with steam, subjecting the diluted material to apreheating at a temperature greater than 750 but less than about 1l000., for a period less than 5 seconds, sufficient to obtain a gasexpansion between about 2-3 and some acetylene formation, but insumcientto cause material carbon monoxide formation, subjecting the preheatedmaterials immediately to a further heating at a higher temperature, butless than 1600 6., and for a shorter period to obtain additional gasexpansion with substantial acetylene formation, and rapidly cooling theresultant gases containing acetylene.

3. A process for the manufacture of acetylene, which comprises dilutinghydrocarbon material capable of forming acetylene and olefines, withsteam at a dilution ratio between about 3-18. subjecting the dilutedmaterials to a preheating at temperatures in excess of 750 C. but lessthan about 1050 C. for less than 5 seconds, in a zone having an arearatio between about 25-100, to obtain some acetylene formation,immediately feeding the preheated product at a temperature within theaforementioned range to a pyrolysis treatment for a fraction of a secondat a higher temperature not greater than about 1600 C. to

obtain a gas expansion of the preheated product to between about 2.5-5,and rapidly cooling the gases containing acetylene which have beenformed.

4. A process for the manufacture of acetylene, which comprises dilutinghydrocarbon material essentially composed of non-acetylenic hydrocarbonssuitable for decomposition into acetylene and olefines, with steam at adilution ratio between about 3-18, subjecting the diluted materials to apreheating at temperatures in excess of 750 C., but less than about 1050C. in substantially noncatalytic metal tubes for a period of timesuflicient to cause the formation of some acetylene but less than 5seconds and insuflicient to cause the formation of more than about 5%carbon monoxide, immediately feeding the preheated product at atemperature within the aforementioned range to a pyrolysis treatment fora fraction of a second at a higher temperature greater than about 1600C. in ceramic apparatus to obtain a further gas expansion of thepreheated product to between about 2.5-5, and rapidly cooling the gasescontaining acetylene which have been formed.

5. A process for the manufacture of acetylene from hydrocarbon materialcontaining volatile sulphur ingredients, which comprises diluting saidhydrocarbon material with steam but only a small amount thereof so thatany steam in the diluent forms a mixture with the hydrocarbon materials,having a dilution ratio less than 6, subjecting the diluted mixture topreheating sufilcient to cause the formation of some unsaturatedhydrocarbon but for less than about seconds, at temperatures betweenabout 800 C. and 1050 C., then without substantial cooling, subjectingthe preheated materials for a fraction of a second to a highertemperature not greater than 1450 C. to obtain a gas expansion betweenabout 2.5-4.2, and rapidly cooling the gases containing acetylene whichhave been formed.

6. A method for the manufacture of acetylene from hydrocarbon materialscontaining small amounts of at least one volatile sulphur ingredient,which comprises diluting the hydrocarbon with steam in a dilution ratioless than about 5, supplementing the steam diluent with another diluentmore inert than steam, preheating the mixture at a temperature greaterthan 800 C. but less than 1000" C. for a period sufflcient to cause somegas expansion but insufiicient to cause substantial carbon monoxideformation, turther heating the mixture in its preheated condition at ahigher temperature less than 1600 C. for a fraction, of a second, andrapidly cooling the acetylene-containing gases produced.

'I. A process for the manufacture of acetylene trom hydrocarbonmaterials, which comprises preparing ahydrocarbon material with anysteam therein in a dilution ratio less than 6, subjecting thehydrocarbon materials to preheating for less than about 10 seconds attemperatures above 800 C. but less than 1100 C., immediately after thepreheat injecting steam into the preheated materials, then subjectingthe materials to ahigher temperature not greater than 1500" C. for afraction of a second; and rapidly cooling the gases containing acetylenewhich have been formed.

8. A process for the manufacture of acetylene by procedure including thepreheating of hydrocarbons in a preheater having a content of nickelwhich under conventional operation would promote undesirable sidereactions, which comprises diluting the hydrocarbon material with steamin a dilution ratio between about 3 and 6, subjecting the mixture topreheating in said nickel-containing preheater at between about 800 C.and 1025 C. for a period suflicient to cause some oleflne formation butfor less than about 5, seconds, substantially immediately subjecting thepreheated mixture to heating at a higher temperature and for a shorterperiod but at a temperature below 1600 C. to cause the formation ofacetylene, and then rapidly cooling the acetylene-containing gases.

9. A process for the manufacture of acetylene by procedure includingpreheating of hydrocarbons in a preheater containing a content or nickelgreater than 2%, which comprises diluting the hydrocarbon material witha small amount of steam to give a dilution ratio less than 6, subjectingthe mixture to preheating in said nickelcontaining preheater at betweenabout 800 C. and 1050 C. for a period which causes some gas expansionbut for less than about 5 seconds, adding further steam to the materialsbeyond the preheating, then subjecting the mixture to heating at ahigher temperature, less than 1600 C., for a fraction of a second, in aceramic reaction zone to cause the formation of acetylene, and rapidlycooling the acetylene-containing gases.

RUDOLPH LEON ARD HASCHE.

/ CERTIFICATE OF CORRECTION. Patent no. 2,256,555.

RUDOLPH LEONARD HASCHEQ It is hereby certified that error appears in theprinted specification of the above' numbered patent requiring correctionas follows: Pagelg, second colimm, line hffor the word "with" read---from-; page 5, second column, line 65, for "splphur" read --sulphur-;page 6, second column, line 52, for "realtion" read -relation--; page 7,"first column, line 50, for "14.0" read --2.0--; and second column, line26, for "carrynig" read --car ry ing page 8, second column, line 20, forsuspectible read -susceptib1'e--; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office.

Signed and sealed this 27th day of May, A. D. 19m.

April 1, 191m.

Henry Van Arsdale (Seal) Acting Commissioner of Patents

